#welcome{
    margin-bottom: 20px;
}
#username{
    color: blue;
}
.wrapper {
    width: 500px;
    margin: 0 auto;
}

.tb{
    margin-top: 20px;
}
.modal {
    width: 100%;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.5);
    position: absolute;
    display: none;
    border: 1px solid red;
}

.modal .form{
    width: 500px;
    height: 400px;
    background-color: #fff;
    position: absolute;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    margin: auto;
    padding: 20px;
    box-sizing: border-box;
}

.modal .form input {
    width: 100%;
    height: 35px;
    margin-bottom: 20px;
}

.modal div span:nth-of-type(2) {
    float: right;
}

.modal .form div:nth-of-type(4) {
    width: 100%;
    text-align: center;
}